The present invention relates to improved apparatuses and methods for feeding gases. More specifically, in one embodiment this invention relates to feeding or supplying a plurality of different types of gases one after another through a single gas feed pipe by switching the gas type from one to another at specific time intervals. In another embodiment, this invention relates to feeding or supplying a single type of gas through one or a plurality of pipes or any combination of pipes in any sequence of switching pipes. With the flow rates controlled by means of a single flow rate controller in semiconductor manufacturing facilities, this offers such advantages as reduction in the size and manufacturing costs of the gas feeder.
In semiconductor manufacturing, many types of gases are used in different ways. For example, a number of different types of gases are drawn, not all at once but one after another in a series fashion by switching the gas type from one to another at specific time intervals. Also, one and the same type of gas is often used at different flow rates simultaneously or in parallel. In those applications, the flow rates must be controlled with high accuracy.
In prior art gas feeding apparatuses for use in semiconductor manufacturing, flow rate controllers such as mass flow rate controllers are installed, one on each gas line, to control the flow rate with high accuracy.
In etching, one of the important processes in semiconductor manufacturing, for example, a plurality of insulating films are etched. This process is made up of a number of etching steps. In each step, 3 or 4 types of gases are used in combination. To supply those gases, prior art gas feeders require a total of more than 10 gas and flow rate controllers in the etching process alone. A vast number of such controllers have to be installed to serve an entire semiconductor manufacturing plant.
In the Chemical Vapor Deposition (CVD) process, a type of gas is supplied to a treatment reactor at one or different flow rates through a plurality of outlets simultaneously to carry out a CVD treatment. The prior art gas feeder has a flow rate controller installed at every outlet line to regulate the flow rates. Here, also, too many flow rate controllers are needed. To a single treatment reactor for the CVD process, in addition, a plurality of types of gases may also be supplied in a series fashion. That likewise requires quite a number of flow rate controllers.
Heretofore, mass flow rate controllers had been the primary flow rate controllers used. In recent years, so-called pressure-type flow control systems have become more common.
The installation of a large number of flow rate controllers not only increases the size of the gas feeder but also makes it difficult to keep down the costs both of the feeder itself and of facility maintenance and service costs. This also presents such problems as increased labor in maintenance and the necessity of keeping many replacement and spare parts in stock, which inevitably raises the running costs of the gas feeder.
The present invention addresses those problems encountered with the prior art apparatuses and methods for feeding gases in semiconductor manufacturing plants, that is, the necessity of installing too many flow rate controllers, one for each outlet line, which has prohibited size reduction of the gas feeding equipment and reduction of the costs of the equipment itself.
It is accordingly a primary object of the present invention to provide an apparatus and method for feeding gases for use in semiconductor manufacturing.
This novel apparatus and method, by means of only a few flow rate controller units, controls many different types of gases or different flow rates of the same gas in semiconductor manufacturing with high accuracy. Moreover, the novel apparatus and method permits a reduction in the size of the gas feeder itself and a substantial reduction in the manufacturing costs of the equipment.
The object of the invention is achieved by installing a single flow rate controller in a single process consisting of a number of steps or a group of common steps in the respective processes, thereby controlling the gas flow rates so as to supply one and the same type of gas or a plurality of different types of gases to each process or step one after another, by switching the gas flow path or gas type from one to another at specific time intervals, and also by making arrangements so that many different types of gases or significantly different flow rates of one and the same gas are dealt with or controlled with high accuracy and supplied through one or a plurality of feed ports.
In each semiconductor manufacturing process or in steps in the process, many different types of gases are used. They are generally used, however, not all at a time but one after another or in a series fashion. That is, the flow of gases to a process is switched from one type of gas to another type of gas at specific time intervals. Even a single flow rate controller can control different flow rates of one type of gas or the flow of a plurality of gases with high accuracy, if the flow characteristics can be automatically switched and compensated or switched and adjusted to cope with the change in gas type or flow rate.
The apparatus for feeding gases for use in semiconductor manufacturing as defined in one embodiment is basically constituted of a plurality of gas supply sources, gas source valves provided on the respective lead-out pipes, a flow rate controller provided on the main gas feed pipe into which the lead-out pipes converge, and a gas feed valve mounted on the outlet side of the flow rate controller. Preferredly, a plurality of units of this apparatus for feeding gas are arranged in parallel and each gas feeder supplies different types of gases as needed to the semiconductor manufacturing facilities.
The apparatus for feeding gases for use in semiconductor manufacturing in another embodiment is basically constituted of a unit of gas supply source, a flow rate controller installed on the main gas feed pipe from the gas supply source, and a plurality of gas feed valves provided on the outlet side of the flow rate controller in the shape of a plurality of parallel branches. Preferredly, a plurality of units of this apparatus too for feeding gas are arranged in parallel and each gas feeder supplies different types of gases as needed to the semiconductor manufacturing facilities.
In both of the above embodiments of the invention, the flow rate controller may be either a mass flow controller or a pressure-type controller.
When a pressure-type controller is used in this invention, the pressure-type flow control system may comprise a control valve CV provided on the main gas feed pipe, a pressure detector 14 provided on the downstream side from the control valve CV, a plurality of orifices 2a, 2b, . . . provided in parallel on the downstream side from the pressure detector 14, a flow rate calculation circuit 20 for calculating the flow rate Qc=KP1 (where K is a constant) from the pressure P1 detected at the pressure detector 14, a flow rate setting circuit 32 for outputting a flow rate setting signal Qs, and a calculation control circuit 38 for outputting the difference between the calculation flow rate signal Qc and the flow rate setting signal Qs as control signal Qy to the drive 8 of the control valve CV. The control valve CV is operated to bring the control signal Qy to zero, thereby controlling the flow rates on the downstream side from the orifices 2a, 2b . . . and at the same time selecting the orifice with the bore matching with the gas flow rate out of the plurality of orifice 2a, 2b . . . and actuating the same.
In the above-described apparatuses, the pressure-type flow control system may be configured so that one or a plurality of orifices are provided in the shape of branches and installed on the downstream side from the gas feed valve. In this case, a plurality of units of the orifice may be provided in the shape of branches at the inlet of or inside of the treatment reactor on the downstream side from the gas feed valve.
Still another embodiment of the present invention is a method for feeding gases for use in semiconductor manufacturing, which method comprises providing a single flow rate controller for gas supply in each semiconductor manufacturing process or in a group of common steps in the processes and wherein, with the flow rates regulated by the flow rate controller, one type or plurality of types of gases are switched and supplied one after another to each process or each common step group at specific time intervals. In carrying out this method, a single type or a plurality of types of gases may be supplied to a single treatment reactor from a plurality of feed ports. Further, in implementing this method, one may work out in advance the flow rate control characteristics of the mass flow controller in the form of data for each type of gas to be supplied and each flow rate, store those data in a storage of a control computer, retrieve the flow rate characteristics matching for the type of gas or flow rate to be switched over to from the computer storage when the gas type or flow rate is switched, and regulate the flow rate of gas according to the flow rate characteristics.
In accordance with the method of the present invention in which the flow rate controller is of the pressure-type, one may work out in advance the flow factor FF in relation to a reference gas (e.g., nitrogen gas) for each type of gas to be supplied and, when the gas type is switched, bring the flow rate specifying signal Qs after the switching to kQe, that is Qs=kQe in which Qe is the flow rate setting signal for the reference gas and k is the flow rate conversion rate.
When the flow rate controller herein is of the pressure-type, it may be provided with a plurality of orifices with different bores in parallel and those orifices may be selectively activated according to the flow rate of the gas to be switched over to.